POS0150 ANKYLOSING SPONDYLITIS RELATED STRUCTURAL CHANGES IN THE SPINE INDEPENDENTLY INFLUENCE PATIENT REPORTED PHYSICAL FUNCTION IN MEN BUT NOT IN WOMEN. A COMPREHENSIVE CROSS-SECTIONAL ANALYSIS OF BATH ANKYLOSING SPONDYLITIS FUNCTIONAL INDEX AND ITS RELATION TO SEX
Authors: M. Hallström, E. Klingberg, A. Deminger, J. Backman Renman, M. Geijer, H. Forsblad-D’elia
Journal: Annals of the Rheumatic Diseases (2022)

Background Patient reported physical function assessed by Bath Ankylosing Spondylitis Functional Index (BASFI) is an important outcome in ankylosing spondylitis (AS) and is associated with health-related quality of life. Objectives To improve health care efforts, we aimed to investigate which demographic and disease related factors that influence BASFI in AS patients overall and stratified by sex. Further, we sought to elucidate if there are differences between sexes regarding specific BASFI items. Methods Patients fulfilling the modified New York criteria for AS were included in two geographically separate regions in Sweden for this observational cross-sectional study. Patients were assessed with 66/68 joint count and Bath Ankylosing Spondylitis Metrology Index (BASMI) measurements. Lateral X-rays of the spine were performed for modified stoke ankylosing spondylitis spine score (mSASSS) and BASFI, BASDAI, ASDAS CRP were registered. Multiple linear regression analyses were used to investigate influencing factors on BASFI. Independent variables were chosen based on what is previously known and on hypothetical reasoning. Models were performed overall and stratified by sex. Results A total of 353 patients, age (median, range) 53 (17-78) years, symptom duration 27 (2-56) years, men 62.3% and HLAB27 91.8 % were included. In multiple linear regression analysis age, BMI, ASDAS CRP, mSASSS, fatigue (BASDAI Q1) and tenderness (BASDAI Q4) were found to significantly associate with BASFI. In models separated by sex, mSASSS independently influenced BASFI in men (p&lt;0.0001) but not in women (p=0.124)(Table 1). Further, separate BASFI items were compared between sexes. The ability to look over shoulder was scored the worst among men while getting up from the floor was hardest for women (Figure 1). Differences between sexes were found in the ability to look over shoulder (p=0.05) and the ability to climb stairs without handrail (p&lt;0.001). Among the separate BASFI items, the ability to look over shoulder showed the highest correlation with mSASSS (r= 0.532, p&lt;0.001). Table 1. Multiple linear regression analysis exploring factors associated with BASFI All Men Women R 2 0.58 0.62 0.54 B (95% CI) p-value B (95% CI) p-value B (95% CI) p-value Age 0.06 (0.04;0.08) &lt;0.0001 0.05 (0.03;0.07) &lt;0.0001 0.08 (0.05;0.11) &lt;0.0001 BMI 0.05 (0.01;0.09) 0.024 0.04 (-0.01;0.09) 0.093 0.05 (-0.03;0.13) 0.209 ASDAS CRP 1.04 (0.74;1.34) &lt;0.0001 0.84 (0.48;1.20) &lt;0.0001 1.39 (0.86;1.93) &lt;0.0001 mSASSS 0.03 (0.02;0.04) &lt;0.0001 0.03 (0.02-0.05) &lt;0.0001 0.02 (-0.01;0.06) 0.124 Fatigue 0.34 (0.24;0.43) &lt;0.0001 0.41 (0.29;0.53) &lt;0.0001 0.27 (0.11;0.42) 0.001 Tenderness 0.17 (0.07;0.26) 0.001 0.14 (0.02;0.27) 0.027 0.18 (0.02-0.34) 0.027 Women -0.29 (-0.74;0.17) 0.214 N/A N/A Figure 1. Separate BASFI items women compared to men Conclusion AS related self-reported physical function measured by BASFI was influenced by disease activity, fatigue and tenderness in both men and women. Interestingly, structural changes in the spine, evaluated by mSASSS, independently influenced BASFI in men but not in women with AS. The ability to look over the shoulder was worse in men vs women and excelled as more disease specific than other individual BASFI items in both sexes. Disclosure of Interests None declared